A mechanism for moving optical elements of an optical system
The present invention relates to a mechanism for moving optical elements of an optical system along the optical axis.
There are optical systems provided with zooming functions, such as some kind of binoculars. Such optical systems vary the magnifying-power by moving two optical lenses, for example, and change the distance between them in the optical axis direction. A lens moving mechanism, used in such optical system to move the lenses along the optical axis, is provided with two lens frames, each for supporting one of the two lenses, and two guiding shafts along which the lens frames move. The guiding shafts are disposed at both side of the lens frames and extending parallel to the optical axes. The guiding shafts are inserted in holes formed on each sides of each lens frame. Thus, each lens frame engages with the guiding shafts slidably so that it can slide, and therefore move the lenses, along the guiding shafts, i.e. parallel to the optical axis.
It is necessary for the lens frames to have the holes for receiving the guiding shafts as long as possible so that each lens frame can be guided precisely without play along the guiding shaft. However, such long holes require longer size of the lens frame along the guiding shafts, which make it difficult to produce a compact lens moving mechanism.
It is therefore an object of the invention to provide a compact mechanism for moving optical elements of an optical system.
A mechanism according the invention is for moving a first optical element and a second optical element along an optical axis of an optical system. The mechanism comprises first and second guiding shafts, a first frame, and a second frame.
The first and second guiding shafts are disposed parallel to the optical axis and spaced apart to each other in a direction perpendicular to the optical axis.
The first frame is movable along the optical axis and supports the first optical element. The first frame includes first front and rear shaft bearings and a second shaft bearing. The first front and rear shaft bearings are disposed spaced apart from each other along the first guiding shaft and are engaged with the first guiding shaft slidably along the longitudinal direction of the first guiding shaft. The second shaft bearing is engaged with the second guiding shaft slidably along the longitudinal direction of the second guiding shaft. It should be noted that a shaft xe2x80x9cbearingxe2x80x9d as described herein includes any kind of shaft receiving structure that supports and/or guides the supported/guided element having the bearing along a shaft (including slide, plain, journal, roller/ball bearings and bushings). The shafts discussed herein need not have a circular cross section.
The second frame is movable along the optical axis and supports the second optical element. The second frame includes third front and rear shaft bearings and a fourth shaft bearing. The third front and rear shaft bearings are disposed spaced apart from each other along the second guiding shaft with the second shaft bearing therebetween and are engaged with the second guiding shaft slidably along the longitudinal direction of the second guiding shaft. The fourth shaft bearing is engaged with the first guiding shaft slidably along the longitudinal direction of the first guiding shaft between the first front and rear shaft bearings.
The first front and rear shaft bearings may be provided with a first front hole and a first rear hole, respectively, into which the first guiding shaft is to be inserted. Preferably, the first front and rear holes are formed to receive the first guiding shaft without play within a plane perpendicular to the optical axis. The second shaft bearing may be provided with a second hole, into which the second guiding shaft is inserted, formed to receive the second guiding shaft with play in a direction substantially perpendicular to the optical axis (e.g., horizontal). For example, the second hole may have a rectangular cross-section of which longitudinal axis is perpendicular to the first guiding shaft.
The third front and rear shaft bearings maybe provided with a third front hole and a third rear hole, respectively, into which the second guiding shaft is inserted. The third front and rear holes are formed to receive the second guiding shaft without play within a plane perpendicular to the optical axis. The fourth shaft bearing is provided with a fourth hole, into which the first guiding shaft is inserted, formed to receive the first guiding shaft with play in a direction substantially perpendicular to the optical axis (e.g., horizontal). For example, the fourth hole may have a rectangular cross-section of which longitudinal axis is perpendicular to the second guiding shaft.
The first frame may have a first extension extending parallel to the first guiding shaft between the first front and rear shaft bearings to support the second rear shaft bearing spaced apart from the first front shaft bearing. Preferably, the first extension has an abutting portion against which the fourth shaft bearing abuts to align the fourth hole with the first front hole and the first rear hole.
The second frame may have a second extension extending parallel to the second guiding shaft between the third front and rear shaft bearings to support the third rear shaft bearing spaced apart from the third front shaft bearing.
Preferably, the second extension has an abutting portion against which the second shaft bearing abuts to align the second hole with the third front hole and the third rear hole.
The first and second guiding shafts are preferably arranged on a plane including the optical axis. Further, each of the first and second optical elements is preferably an optical lens. Further preferably, the first and second optical elements are lenses of a telescope optical system of which magnifying power varies when distance between the first and second optical elements along the optical axis is changed.